Exchange Chambers

A tenant allowed an undertenant into occupation without consent, the landlord then forfeited the headlease for non-payment of rent, but accepted rent from the undertenant. The landlord has now requested that the undertenant bring the property into repair under the terms of the headlease (rather than the less onerous obligations in the underlease) and vacate as negotiations for a direct lease have broken down. Does the undertenant have to comply?

Is there any case law establishing that the competent landlord for the purposes of the Landlord and Tenant Act 1954 must be the legal registered owner? In other words, can a landlord that has been granted an ‘intermediate’ lease be a competent landlord for the purposes of serving a section 25 notice if its interest is still beneficial only (the lease being with HM Land Registry pending registration)?

Where there is a party wall between two pieces of land, and the land on one side is putting pressure on the wall causing it to crack, who is responsible for the repair costs? Would this be different if it wasn't a party wall?